Ok, so after looking at lspci -k and configuring my Gentoo kernel to have some additional modules, there was no difference.

These are the extra things that got loaded -

agpgart 26268 2 ttm,drm -- I dont have an AGP slot in my lap... so this should have been a possible feature of the chipset.
i2c_algo_bit 4823 1 radeon -- I have radeon built into the kernel.
shpchp 28659 0 -- PCI hotplugging, I dont have any additional PCI slots...
pci_hotplug 11274 1 shpchp

Just out of curiosity, not sure it may help, but can you try my precompiled kernel from here. Get this tgz fille and extract it to / (has the kernel file vmlinuz-2.6.36-helium0 in boot/ and modules in lib/modules/2.6.36-helium0/).

As a possible sidenote, are you missing some firmware support inside the kernel? (There should be some radeon related firmware bin files installed by the kernel in /lib/firmware/radeon/, e.g., /lib/firmware/radeon/RS600_cp.bin etc.)_________________Helium Sources || Gentoo Minimal Livecd

It gets loaded onto your graphics card and provides an API for the drivers to use. Without firmware, you have no acceleration of any kind. 300 fps on gears is what you'd expect from purely unaccelerated software rendering.